Signalling system using time-division-multiplex

ABSTRACT

1,147,256. Automatic exchange systems. INTERNATIONAL STANDARD ELECTRIC CORP. 14 Sept., 1967 [17 Sept., 1966 (2)], No. 41990/67. Heading H4K. A plurality of channels carrying V.F. (e.g. dialling) signals are scanned in TDM manner and the results of the scanning are stored in a memory in respective sections thereof reserved for each channel. The contents of each section are then read-out at a much higher rate than they were written-in so as to effectively increase the frequency of the original VF signals whereby they can be analysed by BPF&#39;s having relatively large bandwidths and short transit times. This method is adopted because a centralized control analyzing the high frequency signals can monitor a greater number of channels carrying signals that last for a given time than could a control analysing directly the incoming VF signals. 2-out-of-6 VF signals having a minimum duration of 10 msecs. and occurring on channels S1 . . . Sn are sampled at a 5 kc/s. rate by scanner ZM and the results, after conversion into digital form, are stored in sections of a core store HSP pertaining to each channel. When each channel has been sampled 25 times scanning is stopped for one cycle and all the contents of HSP are read-out during this cycle, corresponding to a read-out rate of 5 Mc/s. Each section is read-out in parallel, via digital/ analogue converter DAW, low-pass filter TP (cut-off 5 Mc/s.) and band-pass filters BF1- BF6 (bandwidth 100 kc/s.), so that a 2 out-of-6 code is written into similar sections of a store (register) RSP. It is ensured that each code contains only two elements by means of a fault detector CU. If incoming signals occur in 2-out-of-8 code, they are analysed and then converted into 2-out-of-6 code by auxiliary filters BF&lt;SP&gt;1&lt;/SP&gt; and converter CW. The above numerical data relates to a system having 20 channels. If the incoming signals have a greater minimum duration then the channels can be arranged in groups and each group then scanned and analysed repeatedly but in turn (Fig. 4, not shown). It is mentioned that the various scanning operations may be controlled by a stored program.

June 2, 1970 H. Roos 3,5l6,07l

SIGNALLING SYSTEM USING 'I'IME-DIVISIONMULTIPLEX Fi1ed ug' 21. 1967 zM, the signal channels 'a1e scanned cyclically and S110' cessively. The Scanner ZM is shown in FI(. 1 as a To[ary Selector, but in Teality it is referably an electronic device sinpe these devices are Sufciently knovvn, there is no need t explain [hem here in deail.

4"^t each Scanning, the In0mentary arIl )litude of the sig- Ilal on the Scanned signal channel is determined. Therefore, the result of each Scanning cycle is obtained in the forn of an arpitude-1T0dulated pulse in the time slot associated with the Scanned Signal channel. (;0rresponding t0 the teachings of the scanning theorem, the maximum duration of a Scanning cycle Should be equal to half the period of the maxi[nun| frequency to be evaluated.

The pulses furnished by the scanner are fed into an anagto-digita1 converter ADW vvhich provides an 0ut put in the form of a code signal indicating the a[nplitude value F()l' exanple, the output Signal Inay be a pulse code which is fed illt0 the St()re circuit HSP. That Store circuit IIS1 COInprises a n]enory rovv (l' a partial store circuit for each sig!la1 channel S1 t0 S. Each part of the Store circuit is further SubdVided into a nunber of Store sections The infortnation Signals arriving on a Sig- Ilal channel are individually stored in succeeding Store sections of the partia Store associated with the Sig!a channel. The advancing fron partial store to partial Store is Synchronized with the advance of the Scanner ZM Te- Sponsive '0 Signals sent via the signal vvire A Which extends hetween the scanner ZM and the stores HSP and RSP FIC}. 2 shows an example of how a partial Store or Inemory TOW is organized in circuit I ISP Ihe lode of 'C bits representing the individual an]pitude inf()rlTlations are stored in the Store Sections zl and Z'( 0f the partial St0e circl1it. Therefore, each bit compr...ses Severa storing elements (e g( fnagnetic cores). The rSt Store secuon IA provides an interna address( T'his address is in the frSt instance, th Store Section zl in the non-0peraive condition of zl' After the HISt Scanning cycle, the interna address zz is entered in the store Section TA, etc. By using the internal address registered in the Store Secion as an address for the next following Store section to be used, the continuous Storing of the Successively obtained inforn1ations for this signal channel iS controlled. It is, Of course, vvithin the scope of the present invention to ISe other stores and control nethods' After a number of N cycles (dimensioning of N is ex- )1ained latel) the partial stores are read Successively. Thus, the bits of information included in the individual artial store Sections zl 0 z'( 0f the circuit I-ISP are successively fed into a digita-t()-ana10g converter ])Aw which useS each bit of infornation to reconstruct the orig inal Sample' These reconstructed satnples ate fed through a lovv-paSS-f...lter which generates fronl these salnples a continuous analog signal again However, the clock frequency at Which the inforn1ation bits are read fronl the Store, is a nultiple of the Scanning frequency (z), at Which the scanner ZM operates The[efore, each fre quency, included in the 0iginal Signal, iS mutipied in the relation 'Z`/ (1).

Perhaps a nu[nerical exaInple T]ay explain this a little better AssuIne that the Signal channels Sls are lines on vvhich Signals appear in a 2out-0f-6 frequency code' The highest of the six frequencies used in the code is 2 kc./S., d]e10westfrequency is 1 kc./s' (:0r respondingy, the longest period (Zg) lasts for 1 mini- Second, the shortest eriod (Z() for o 4 Tillisec01d Ac cording to the Scanning theore[n, the duration of a Scaning cycle can be TZ= (=0.2 n!illisecond at a maxi T[lum. 4^t a technically reasonable scanning period per channel of 10 sec( 20 channels can be scanned vithin a Single cycle The cycling period 0f TZ=0,2 1Tillisecond Ineans a Scanning frequency kc./S'

The time required to read a store Secion of a partial Stole iS 0-2 LSc., Which IneanS tlat a reading clock fre quency is mc(/s. I'lle frequency Ilulti;)lying factor is then j'r/ Z)=l000 At the out ut of the lter TP, a

4 Signa1 appears which may c0mprise 2 Inc./s' aS Irlainum frequency and 1 mC./S, as T1iimum frequency T'his sigla iS fed to Six frequency-Selective band-pass lterS BF1 to BF6, each of Which is tuned t0 1000-times the value 0f the associated frequency of the OW-frequency code For a proper separaion of the Six frequencies in the range of l mc./S. to 2 rnc(/S., a bandwidth of kc,/S is quite acceptable' Therefore, assuming tha the transient time of each fltc1 corresponds appr0xin1ately to the recipr0ca value of twice itS bandwidh, the transient time 0f the lter is appr0ximately j Sec. The Signal fed t0 the band-passnlters BF1 to BF |Tlust, therefore, have a 1Tiimun duration of Sec.

An advantage of the invention is clearly Shown. Filters vvith a bandwidth of approxixnatey 100 c./S. Would be required if the evauation Were Inade directy in the lowfrequency range These filters would have a transient time of approximately j Iniiseconds. This rneans that, during a cyclical Scanning, at least j miniseconds should be pro vided for each line scanned( In general, f() a roper recognition of each Signal by neans of Scanning, the Ininilnun1 signal length 1Tllst be at least equal to the duration of Scanning cycle. Therefore, at a maxinlum, two channels could be Served by one evauating device for a sig lal length of 10 n1i1iseconds, vvhich Ineans that a centralization cann0t be perforned thereby As will be del10nstrated, the conditions are substantially n0c favorable when the invention is used( In order to guarantee that the signals applied to the band aSS-lterS BFl to BF6 Will have a mininurl duration of j Sec., at least N=2 amp...ude values must be SOred before an evaluation is Tnade This nunlber (N of the cycles) is calculated aS fonows:

(l) The duration of a j Sec Signal after the fre quncies have been increaSd 1000-times corresponds to a duration of j [11illiseconds of the 0rigina Signal; (2) For the maxinlm frequency =2 kc /S'), a period of Z'(=0'4 n]"lisecond equals lz j periods; (3) Sinc the lines are scanned twice per period of the Tnaxinlun frequency, 25 Scanning cycles occur during the five I1illi- Second peri(d where I(=the frequency m11iplicati()[1 factor,

T`"=the tralsient time of one of the highfrequency filters used,

ZZ')=the duration of one period ()f the Scanning frequency,

)`#:the reading clock frequency,

After 1=2 Scanning cycles, the partial Stores can be read-out( ^AS a partial store is read in Sec. and the entire Store IISP, COInprisi[1g 20 Iarial Stores, can be read in 100 Sec', a reading cycle of 0 2 l11illisecond duration is adequate after each 2 Scanning cycles.

Control of the reading )r(cess is paricuary Simple. The address of the parual store to be read by tlle Scan Ilel ZM is furnished via the Siglalling Wire z This ad dress Inay als0 be forwarded t() a!1 0utput store I(SP Wvhich has (ike the Store HSP) a partial Store for each signal channel that is used to receive the inforination bits whicll are to be evaluated Moreover, the store Section IA (FIG. 2) ITlay be replaced by an address counter whic1 is common to all partial Stores of the memory IISI' If provided, this address c0un is advanced one SJe afer each cycle of the Scanner ZM' After evaluating the contents of the partial Store in the Store IISP, the address counter iS e[ased.

Therefore, a complete evaluating process c0rresponds to the duration of 25 Scanning cycles for Storing plus one scanning cycle for reading. At a scanning cycle period Of z' 'TTle system of claim l Wherein said Signa frequency converting means conTprisEs, firs nlernory means for storing ampntude values found during a plurality 0f successive scanning cycles, Said first men0ry rneans incuding St0res which are individually associated vvith the signa channels, means for reading out said stores at individua time S0ts responsive 0 a reading clock frequency higher than the Scanning frequency after a denned number of scanning cycles at least equal to he roduct of the transien 'il'le of a ler and the reading c10ck frequency, digital to analog converter means operaed responsive t0 Said reading neans for f(rning analog Signals ()llt of the inforn]ation Wh...ch is read out and evaluating n]eans conprising frequency-Sclec[ive circuits for evaluating said Signals.

3. The system of claim z, Characterized in this hat analog to digital converter means are provided to convert the signal an1plitude Values to a code for Storage 4- The invention of claim 2 including OW frequency filter means interposed beween the signal channels and the fTequency-selecive circuits for evaluating said signals.

S 'lhe invention of clain z characterized in this tha Stored scanning program nleans are provided for contr()|ling he scanning of the signal channels The invention of caim 2 characterized in this that the Signal channls are Subdlvided int0 groups, a pluraiy of rSt scanning means for Scanning associated ones of Said groups of signa channels in groups corresponding to their Subdivisi03, each group being Scanned for a predeterfnined nu[nbe ()f cycles, cascaded Scanning rneans for scanning said first Scanning Ineans, evaluation circuit means for nlaking an evauaion of Said an1;)]itude vaues, and Said evaluation circuit means including ouput storage rrleans for storing Said evaluation in a artial Storage of an outpu Store provided for the signal channes of said group( 7. The invention of clai[n 6 characterized in this that Switch means are rovided for seectively contro1ing Said evaluating circuitry t0 acc0mn10date diferent code signals RefeeucGs Ced UNITED STATES PATENTS 3 3ll,707 3/I967 UrquhartPuuen 1791 RAULFE B ZACHE, Primar Examiner 

